1. Field of the Invention
The present invention relates to a voltage generation circuit of a semiconductor memory device and, in particular, to a voltage generation circuit of a semiconductor memory device for generating a multi-step pulse.
2. Background of the Invention
In general, a variety of voltages are required at the time of operation of programming, erasing and verifying of a flash memory. For example, in case of programming a flash memory cell, a voltage of 9V is applied to a control gate electrode, a voltage of 5V to a drain, and a voltage of 0V to a source.
These voltages can be obtained by a multi-step pulse generator. The multi-step pulse generator has a charge pump, a voltage divide circuit which is connected to an output of the charge pump and to which a plurality resistors are connected in series according to a condition of switches, and a differential amplifier for controlling the output of the charge pump according to an output of the voltage divide circuit. A voltage outputted from the voltage divide circuit and a reference voltage V.sub.REF are compared at the differential amplifier, and according to the result, the charge pump performs a pumping operation in multi-step and generates the multi-step pulse.
However, the voltage generation circuit described above has a problem in that the reliability of the semiconductor memory device is degraded since a leakage current can occur through a plurality of resistors and whereby a ripple can occur to the output voltage of the charge pump.